The River Tolka has been named among six of the most polluted rivers in Ireland according to the Environmental Protection Ageny.

It also revealed that the number of pristine waterways in the country fell to 21 in 2015 - down from 38 in 2009 and 500 in the late 1980s.

In its first six-year review of water quality under new European rules, the Environmental Protection Agency (EPA) warned that Ireland has failed to meet its clean-up targets.

The other severely polluted rivers included the Avoca in Co Wicklow; the Aughboy in Co Wexford; the Bredagh near Moville in Co Donegal; the Laurencetown stream in Co Galway; and the Srah river which runs into Lough Mask near Tourmakeady in Co Mayo.

The review showed some improvements in water quality as 19 rivers were classed as badly polluted in the 2007-2009 period.

The report also noted an increase in the number of reported fish kills, with 97 reported between 2013 and 2015, up 27 on the 2007-2009 period.

It said the reason is unclear but it may be due to extended dry spells and/or flooding events rather than increasing serious pollution spills that would have been the main cause of fish kills in the past.

The review found that the national target of 13% improvement in water status for the six-year period had been missed.

It said hundreds of water bodies around the country failed the tests, cancelling out the improvements in water status at a similar number of water bodies in other parts of the country.

Overall, 91% of groundwater bodies, 57% of rivers, 46% of lakes, 31% of estuaries and 79% of coastal waters were found to be of good quality under the EU directive.

Earlier this year the European Commission said it was taking Ireland to court after repeated warnings over the pumping of raw sewage into rivers and the sea.

It said more than 30 towns and cities have inadequate treatment plants for waste water, putting human health at risk, and leaving the country potentially liable for millions of euros in anti-pollution fines.